Question

For an endothermic reaction, energy of activation is $E_a$ and enthalpy of reaction of $\Delta H$ (both of these in $kJ/mol$). Minimum value of $E_a$ will be:

• A. less than $\Delta H$
• B. equal to $\Delta H$
• C. more than $\Delta H$
• D. equal to zero

Answer 1

The correct option is A less than $\Delta H$

For an endothermic reaction

$\Delta H=E_{af}-E_{ab}$

$E_{af}=$ Activation energy for forward reaction

$E_{ab}=$ Activation energy for backward reaction

or $E_{af}=\Delta H+E_{ab}$

So $E_a>\Delta H$